Bean Ryan touched down for the Sharks' opening try in the eighth minute but replays later showed it was scored on the seventh tackle and awarded by referees Matt Cecchin and Henry Perenara.

NRL referees coach Daniel Anderson admitted at half-time that the on-field officials had made a mistake and it is unlikely either will be involved in the remainder of the finals.

The NRL has announced it will hold an inquiry to investigate how the mistake was made.

"What is most concerning is that there are checks and balances across the entire squad to safeguard against the referees making such a mistake," NRL head of football Todd Greenberg said in a statement.

"We don't want this happening again.

"We can't take points away or change a result of a match due to such a decision but we do have to be able to reassure players and fans that this won't happen again in any game."

With the Cowboys handing over possession near the Sharks' line via a Robert Lui grubber kick, Cecchin lost track of the tackle count, calling "four" at what should have been the fifth tackle.

We didn't have any idea, it's the first time I've heard about it. We can't do anything about it.

Antonio Winterstein

Prop Sam Tagataese produced a barnstorming run on what should have been the sixth tackle, before a some splendid Todd Carney vision resulted in Ryan crossing out wide.

The Cowboys' Antonio Winterstein said at full-time his team-mates were not aware of the seventh tackle, adding there was nothing they could do about it now.

Jason Taumalolo crossed seven minutes later and the Cowboys were back in front, but the Sharks fought back with Tagataese going over after Luke Lewis and Gordon combined to get their side within striking distance.

Gordon missed a conversion he should have made and the Sharks trailed 18-16 and, despite Carney clearly hampered by his dodgy hamstring, they went over again when an ugly Jeff Robson pass found Sosaia Feki.

There was still life in the Cowboys, who stopped the clock at 41 seconds near their own line when they packed a quick scrum.

They marched downfield and looked like they had stolen it at the death when Cecchin awarded a try to Kane Linnett only for the replay to show John Morris had pushed his leg of the Cowboys centre over the sideline in an epic finish.